System for non-destructive testing of composites

ABSTRACT

Embodiments are disclosed for characterizing and quantifying composite laminate structures. The embodiments take a composite laminate of unknown ply stack composition and sequence and determine various information about the individual plies, such as ply stack, orientation, microstructure, and type. The embodiments distinguish between weave types that exhibit similar planar stiffness behaviors, but produce different failure mechanisms. Individual ply information is then used to derive the laminate bulk properties from externally provided constitutive properties of the fiber and matrix, including extensional stiffness, bending-extension coupling stiffness, bending stiffness, and the like. The laminate bulk properties are then used to generate a probabilistic failure envelope for the composite laminate. In some embodiments, ply stack type and sequence are also determined for a curved composite laminate using the disclosed embodiments by adding a rotational stage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority from the following USpatent applications. This application is a continuation of U.S. patentapplication Ser. No. 17/006,290, filed Aug. 28, 2020, which is acontinuation of U.S. patent application Ser. No. 14/848,009, filed Sep.8, 2015, which is a continuation-in-part of U.S. patent application Ser.No. 14/386,449, now U.S. Pat. No. 10,697,941, filed Sep. 19, 2014, whichis a National Phase Entry of International PCT Application No.PCT/US2013/033187, filed Mar. 20, 2013, which claims the benefit ofpriority from U.S. Provisional Patent Application No. 61/613,482, filedMar. 20, 2012. U.S. patent application Ser. No. 14/848,009 also claimsthe benefit of priority from U.S. Provisional Patent Application No.62/047,524, filed Sep. 8, 2014. Each of these documents is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention disclosed and taught herein relates generally to a methodand system of automatically identifying and characterizing compositelaminate structures, or laminates, using ultrasonic non-destructivetesting (NDT) techniques. More specifically, the invention disclosedherein relates to a method and system of automatically detecting eachlayer, or ply, of material in a laminate and determining the bulkproperties of the laminate based on the properties of the constituentplies in order to generate a failure envelope for the laminate. Theinvention disclosed and taught herein also relates to a method andsystem of simulating an ultrasonic scan of the individual plies of alaminate.

DESCRIPTION OF THE PRIOR ART

Composite laminates, or laminates, are typically composed of individuallayers of materials that have directionally dependent materialproperties. Each layer is commonly known as a lamina or ply, and theplies are combined in layers to create a bulk structure that forms thelaminate. Knowledge of the individual lamina configuration is importantbecause of the significant effect each lamina has on the finalproperties of the laminate. For example, in unidirectional fiberorientation plies, the ply is considerably stronger in the fiberorientation direction than in any other direction. The choice oforientation, thickness, stacking sequence, or other property of a laminawithin the final composite, will drastically alter the final processedmaterial properties of the laminate.

Composite laminates are used extensively in a variety of structuralapplications and in numerous industries. For example, carbon fiberreinforced polymers/plastics (CFRP) are a commonly-used type ofcomposite laminates in the aerospace, automotive and other industries.Although CFRPs are relatively expensive, their superiorstrength-to-weight ratios make them more desirable than other types ofmaterials. This is reflected by the widespread and steadily increasinguse of CFRP components in fixed and rotary wing airframes, for example.Alternatively, a large industry exists that implements alternativereinforcements sacrificing the ultimate tensile strength for otherdesign parameters such as cost, processing ease, etc. Commonly employedfibers include, but are not limited to, fiberglass, Kevlar, aramid, andother synthetic fibers, as well as a wide variety of natural fibers usedas fillers.

Manufacturing carbon fibers usually involves a process where a singlecontinuous carbon fiber filament is constructed with a diameter ofroughly 0.005 mm to 0.010 mm. For the type of high-quality products usedin aerospace applications, a typical fiber diameter will be on the orderof 0.005 mm. These filaments are 93% to 95% carbon and have a linearmass of roughly 6.6 grams per meter (g/m). Individual filaments are thenwound into a “tow” (i.e., thread or ribbon) that are then used forvarious applications. Typical tows have between 3,000 and 12,000filaments depending on the product application. A 3,000-filament tow hasa linear mass of about 0.2 g/m and are between 0.375 mm and 1.5 mm wideand between 0.2 mm and 0.05 mm thick. By comparison, the diameter of anaverage piece of thread is approximately 0.375 mm for a 3,000-filamentthread.

The tows are woven into a pattern and then impregnated with resin toform an individual lamina that are then stacked on other laminas tocreate a composite laminate layup. The main geometries for an individuallamina are: Percent Warp =percent of orthogonal fibers by weight (where0% means fibers are unidirectional, and 50% means fibers are woven);Areal Density=g/m² of fiber in a given lamina; Thread Count =number ofindividual fiber threads in an individual tow; Tow Width=width in mm ofan individual tow; Layer Thickness=thickness of an individual lamina inmm. In contrast, the main geometries for a completed composite layupare: number of laminas, fiber orientation of individual lamina, thelamina type (i.e., woven versus non-woven, woven type, material makeup),and layup method of individual layers.

The need to repair and modify laminated composites has stretched thecapability of existing non-destructive inspection (NDI) techniques.Specifically, to properly modify or repair laminated composites,sufficient fidelity of the underlying microstructure of the compositeplies is required to understand the baseline (i.e., unmodified,unrepaired) structure, identify and quantify any as-installedmodifications, and analyze the as-installed components for FAA,automotive, and other industry certifications.

In addition, the manufacturing process for composite laminates, as forother materials, inherently includes some variability that affects theperformance of the final part. As such, it is desirable to account forthese manufacturing uncertainties and tolerances when quantifying theexpected structural response of composite laminates. It is alsodesirable to quantify the impact of manufacturing defects and varyingmaterial properties on a composite laminate's performance. Conversely,if the configuration of a composite laminate is determined within somedegree of confidence, it is desirable to quantify the expectedstructural response and life expectancy of that laminate.

Having the ability to detect manufacturing, installation, or usageeffects on a composite laminate, with resolutions on the order ofindividual lamina dimensions and as a function of affected lamina layer,also minimizes modification and maintenance design conservatism orsafety margins, leading to reduced manufacturing, installation, and testcosts.

The ability to quantify a composite laminate's expected structuralresponse is particularly useful where the manufacture's data andinformation about the composite laminate are limited or perhapsunavailable. The problem is compounded by the need in many instances toascertain the composite laminate's as-fabricated structuralcharacteristics, including stiffness, failure envelope, and the like,without performing destructive testing.

Accordingly, what is needed is a system and method for identifying andcharacterizing a composite laminate's internal structure usingultrasonic NDT techniques. More particularly, what is needed is a systemand method for quantifying the composite laminate's expected structuralresponse based on the assessed properties of the individual laminas.

SUMMARY OF THE INVENTION

Embodiments of the invention provide a system for characterizing andquantifying composite laminate structures. The system takes a compositelaminate of generally unknown ply stack composition and sequence anddetermine various information about the individual plies, such as thenumber of plies, ply stack sequence, ply orientations, and the like,based on simulated or actual data representing a scan of the compositelaminate. This information, along with information regarding the typesof plies and the ply constitutive properties, such as resin type, curecycle, and specific type of fiber, is then used to determine a plyfailure load. The information about the plies is also used to derive thelaminate bulk properties, such as extensional stiffness,bending-extension coupling stiffness, bending stiffness, and the like.The laminate bulk properties are then used to generate a probabilisticfailure envelope for the composite laminate. Such a system allowsfacility owners and operators in various industries to assess, support,and maintain composite laminate structures, particularly old and agingstructures, independently of the original manufacturing failureinformation or predictions for the composite laminate structures. Thesystem further provides the ability to perform non-destructive qualityassurance (QA) to ensure, for example, that individual lamina layup wasaccomplished according to design specifications.

In some embodiments, the scan data used in the above method and systemincludes ultrasonic scan data. The ultrasonic scan data is generated byan ultrasonic image simulator, or the scan data is real data captured byan actual C-scan or equivalent type system. In other embodiments, thescan data used in the above method and system is acquired using X-raysignals, radio signals, acoustic signals, and the like.

In general, in one aspect, the disclosed embodiments are directed to acomputer-aided non-destructive method of quantifying individual laminasin a composite laminate. The method comprises receiving composite scandata by a processor, the composite scan data representative of acomposite scan of the composite laminate, the composite scan dataindicating, for each one of an array of spatial locations across asurface of the composite laminate, signal intensity and signaltime-of-flight for a signal reflected and refracted off materialtransitions within the composite laminate. The method also comprisesdetermining one or more lamina properties by the processor based on thecomposite scan data, the one or more lamina properties including numberof individual laminas, fiber orientation of each individual lamina, plytype, including unidirectional or weave, weave type, and thickness ofeach individual lamina. The method further comprises calculating afailure load for the individual laminas by the processor based on theone or more a-priori known lamina moduli and failure parameters. Aprobabilistic failure envelope is then estimated for the compositelaminate by the processor using one or more of the lamina failureparameters.

In general, in another aspect, the disclosed embodiments are directed toa computer system for non-destructive quantifying of individual laminasin a composite laminate. The computer system comprises a processor and astorage device connected to the processor. The storage device stores anapplication thereon for causing the processor to receive composite scandata into the computer system. The composite scan data is representativeof a composite scan of the composite laminate, the composite scan dataindicating, for each one of an array of spatial locations across asurface of the composite laminate, signal intensity and signaltime-of-flight for a signal reflected and refracted off materialtransitions within the composite laminate. The application stored on thestorage device also causes the processor to determine one or more laminaproperties based on the composite scan data, the one or more laminaproperties including number of individual laminas, fiber orientation ofeach individual lamina, ply type, including unidirectional or weave,weave type, and thickness of each individual lamina. The applicationstored on the storage device further causes the processor to calculate afailure load for the individual laminas based on the one or more laminaproperties. A probabilistic failure envelope for the composite laminateis then estimated using one or more of the lamina properties and thefailure load for the individual laminas.

In general, in yet another aspect, the disclosed embodiments aredirected to a computer-readable medium containing computer-readableinstructions for instructing a computer to perform non-destructivequantifying of individual laminas in a composite laminate. Thecomputer-readable instructions comprise instructions for causing thecomputer to receive composite scan data, the composite scan data beingrepresentative of a composite scan of the composite laminate. Thecomposite scan data indicates, for each one of an array of spatiallocations across a surface of the composite laminate, the signalintensity and signal time-of-flight for a signal reflected and refractedoff material transitions within the composite laminate. The computerreadable instructions also comprise instructions for causing thecomputer to determine one or more lamina properties based on thecomposite scan data, the one or more lamina properties including numberof individual laminas, fiber orientation of each individual lamina, plytype, including unidirectional or weave, weave type, and thickness ofeach individual lamina. The computer readable instructions furthercomprise instructions for causing the computer to calculate a failureload for the individual laminas based on the one or more laminaproperties. A probabilistic failure envelope for the composite laminateis then estimated using one or more of the lamina properties and thefailure load for the individual laminas.

These embodiments provide a solution that is useful in a number ofindustrial and manufacturing areas, including quality control, forexample. Other areas that benefit from the disclosed embodiments includeapplications in the field of ultrasonic detector design. Still otherareas benefiting from the disclosed embodiments are able to be developedby those having ordinary skill in the art.

In some embodiments, ply stack type and sequence is also determined fora curved carbon fiber composite using the disclosed embodiments byadding a rotational stage to the transducer. The curved carbon fibercomposite has planar curvature, such that the rotational stage need onlyrotate the transducer about one rotational axis, or it has a sphericalcurvature, such that the rotational stage needs to rotate the transducerabout two or more rotational axes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary system and method for characterizingcomposite laminate structures in accordance with one or more embodimentsdisclosed herein.

FIG. 2 illustrates the exemplary composite laminate characterizationsystem of FIG. 1 in more detail in accordance with one or moreembodiments disclosedherein.

FIG. 3 illustrates an exemplary laminate characterization application inaccordance with one or more embodiments disclosed herein.

FIG. 4 illustrates an exemplary ultrasonic image simulator that is usedwith the laminate characterization application in accordance with one ormore embodiments disclosed herein.

FIG. 5 illustrates an exemplary graphical user interface for theultrasonic image simulator in accordance with one or more embodimentsdisclosed herein.

FIG. 6 illustrates an exemplary flow chart for simulating an ultrasonicimage in accordance with one or more embodiments disclosed herein.

FIG. 7 illustrates an exemplary flowchart for detecting ply propertiesin accordance with one or more of the embodiments disclosed herein.

FIG. 8A illustrates an exemplary ply thickness plot in accordance withone or more of the embodiments disclosed herein.

FIG. 8B illustrates an exemplary ply thickness plot in accordance withone or more of the embodiments disclosed herein.

FIG. 9A illustrates exemplary ply orientations in accordance with one ormore of the embodiments disclosed herein.

FIG. 9B illustrates exemplary ply orientations in accordance with one ormore of the embodiments disclosed herein.

FIG. 10A illustrates an exemplary scatterplot of ply orientations inaccordance with one or more of the embodiments disclosed herein.

FIG. 10B illustrates a histogram of ply orientations in accordance withone or more of the embodiments disclosed herein.

FIG. 11A illustrates an unfiltered exemplary histogram of plyorientations in accordance with one or more of the embodiments disclosedherein.

FIG. 11B illustrates a scatter plot of ply orientations in accordancewith one or more of the embodiments disclosed herein.

FIG. 12A illustrates the filtered version of FIG. 11A showing anexemplary histogram of ply orientations in accordance with one or moreof the embodiments disclosed herein.

FIG. 12B illustrates the filtered version of FIG. 11B showing anexemplary scatter plot of ply orientations in accordance with one ormore of the embodiments disclosed herein.

FIG. 13A illustrates an exemplary spreadsheet of ply properties inaccordance with one or more of the embodiments disclosed herein.

FIG. 13B illustrates a scatter plot of ply properties in accordance withone or more of the embodiments disclosed herein.

FIG. 14 illustrates an exemplary flowchart for determining a laminatefailure envelope in accordance with one or more of the embodimentsdisclosed herein.

FIG. 15 illustrates an overview of the ultrasonic NDT techniques inaccordance with one or more of the embodiments disclosed herein.

FIG. 16 illustrates an example of a transducer used to obtain a C-scanpoint on the surface of a pipe in accordance with one or more of theembodiments disclosed herein.

FIG. 17A illustrates a system with rotational stage in accordance withone or more of the embodiments disclosed herein.

FIG. 17B illustrates front and side views of the system with rotationalstage in accordance with one or more of the embodiments disclosedherein.

FIG. 18 illustrates a graphical representation of a normal vector inaccordance with one or more of the embodiments disclosed herein.

FIG. 19 illustrates an A-scan of a pipe obtain in accordance with one ormore of the embodiments disclosed herein.

FIG. 20 illustrates a graphical representation of the pipe surface inaccordance with one or more of the embodiments disclosed herein.

FIG. 21 illustrates an exemplary schematic of a system with a sensor fororientating to a surface.

DETAILED DESCRIPTION

The drawings described above and the written description of specificstructures and functions below are presented for illustrative purposesand not to limit the scope of what has been invented or the scope of theappended claims. Nor are the drawings drawn to any particular scale orfabrication standards, or intended to serve as blueprints, manufacturingparts list, or the like. Rather, the drawings and written descriptionare provided to teach any person skilled in the art to make and use theinventions for which patent protection is sought. Those skilled in theart will appreciate that not all features of a commercial embodiment ofthe inventions are described or shown for the sake of clarity andunderstanding.

Persons of skill in this art will also appreciate that the developmentof an actual, real commercial embodiment incorporating aspects of theinventions will require numerous implementation-specific decisions toachieve the developer's ultimate goal for the commercial embodiment.Such implementation-specific decisions include, and likely are notlimited to, compliance with system-related, business-related,government-related and other constraints, which vary by specificimplementation, location and from time to time. While a developer'sefforts might be complex and time-consuming in an absolute sense, suchefforts are nevertheless be a routine undertaking for those of skill inthis art having the benefit of this disclosure.

It should also be understood that the embodiments disclosed and taughtherein are susceptible to numerous and various modifications andalternative forms. Thus, the use of a singular term, such as, but notlimited to, “a” and the like, is not intended as limiting of the numberof items. Similarly, any relational terms, such as, but not limited to,“top,” “bottom,” “left,” “right,” “upper,” “lower,” “down,” “up,”“side,” and the like, used in the written description are for clarity inspecific reference to the drawings and are not intended to limit thescope of the invention or the appended claims.

As alluded to above, the disclosed embodiments relate to a system forcharacterizing and quantifying a composite laminate microstructure. Ingeneral, the system is used to derive a 3-dimensional model of thecomposite laminate structure, both the overall shape and the internalstructure. This 3-dimensional model, which includes and otherwiseaccount for inherent variability and tolerances in the laminatemanufacturing process, is then used to determine the properties andcharacteristics of the composite laminate.

In some embodiments, the 3-dimensional model is generated using a scanof the composite laminate. This scan is an ultrasonic scan in someimplementations, or it is a scan based on other types of signals, forexample, X-ray, radio waves, sound waves, and the like. The scan, orrather the data representing the scan, is acquired using a real detectoroperating on an actual physical sample, or it is generated using avirtual or simulated detector instead. Thereafter, certain propertiesand characteristics of the composite laminate are determined from thescan to allow an assessment of the composite laminate without the needfor the original or OEM (original equipment manufacturer) or MRO(maintenance, repair, and operations) records.

FIG. 1 illustrates an example of a composite laminate characterizationsystem 100 in accordance with the disclosed embodiments. In theexemplary embodiment of FIG. 1 , the composite laminate characterizationsystem 100 is an ultrasonic system 100, although as mentioned above, anX-ray system, radio wave system, sound wave system, and the like, arealso used without departing from the scope of the disclosed embodiments.

Among its various functions, the laminate characterization system 100 isused to perform NDT and/or NDI on a composite laminate sample 102 todetermine and quantify its properties and characteristics, symbolized bythe image shown at 104. In basic operation, the composite laminatecharacterization system 100 receives scan data representing ultrasonicresponse signals that have traveled through and are subsequentlyreflected back from the composite laminate sample 102. Based on the scandata, the laminate characterization system 100 derives and ascertainscertain information about the properties and characteristics of theplies making up the composite laminate sample 102. Such properties andcharacteristics include, for example, the ply fiber orientation, plythickness, defect locations, and the like.

In some embodiments, the scan data for the composite laminate sample 102includes A-scans, B-scans, or C-scans. An A-scan is generally understoodto be a measure of the amplitude and flight time (or travel time) of theultrasonic signals reflected along the Z-axis (or depth direction) ofthe sample 102 over the surface (or X-Y plane) of the sample. The A-scangenerally indicates the presence of various features and defects in thesample. In graph form, the A-scan usually has the signal energydisplayed along the vertical axis and the signal flight time displayedalong the horizontal axis.

B-scans, on the other hand, provide a profile or cross-sectional sliceof the sample. In a B-scan, the graph typically displays the intensityof the returned signal as a function of depth along a linear elementwhich is typically along either the X or Y direction, displayed alongthe horizontal axis. The intensity information provides across-sectional view showing where various features and defects arelocated in that cross-section of the sample.

C-scans provide a plan or top view of specific layers or depths withinthe sample. Such scans are used to identify the location (i.e., the Xand Y coordinates) and size of any features or defects within thesample. In graph form, this is usually displayed with the Y coordinatesalong the vertical axis and the X coordinates along the horizontal axis.C-scans are typically produced with an automated data acquisition systemand usually involve a computer controlled scanning system, or the like,to capture reflected signals at each point along a predefined grid overthe surface of the composite laminate sample.

The laminate characterization system 100 accepts scan data from a real,commercially-available ultrasonic detector 106, such as those availablefrom US Ultratek, Inc., of Concord, Calif. An alternative approachincludes using an A-scan system configured to translate the transducer,or alternatively the sample being scanned, in space with scans atspecific locations. These selective A-scans are then collected in thelaminate characterization system 100 to create a C-scan. The laminatecharacterization system 100 also accepts scan data generated by anultrasonic image simulator for purposes of testing and validating thesystem. Such simulated data tends to be cleaner and more free of noiseand artifacts than real scan data from a physical sample and thereforemore useful in some cases, for example, in initializing, configuring,and fine-tuning the laminate characterization system 100.

As mentioned above, in normal operation, the laminate characterizationsystem 100 receives an ultrasonic scan of the composite laminate sample102. This scan data indicates, for each one of an array of spatiallocations on a surface of the composite laminate sample, the signalintensity and signal time-of-flight for a signal reflecting off thelayers or plies within the composite laminate sample 102. The laminatecharacterization system 100 then determines one or more properties forthe individual plies making up the composite laminate sample 102. Plyproperties include, for example, the number of individual plies,orientation of each individual ply, thickness of each individual ply,lamina type (unidirectional or weave), weave type, and total thicknessof the composite laminate sample. Thereafter, the laminatecharacterization system 100 is used to calculate one or more bulkproperties for the composite laminate sample 102 given the appropriateconstitutive stiffness values of the fiber and the matrix along withtheir respective failure parameters, including extensional stiffness,bending-extension coupling stiffness, and bending stiffness, based onproperties for the individual plies (e.g., resin type, cure cycle,specific type of fiber, etc.). Once the bulk properties have beendetermined, this information is then processed by the laminatecharacterization system 100 to estimate a probabilistic failure envelopefor the composite laminate sample 102.

In some embodiments, the laminate characterization system 100 isimplemented as a general-purpose computer, as depicted in FIG. 1 , or itis implemented as a dedicated computer that has been custom developedfor the purpose. In other embodiments, the laminate characterizationsystem 100 is implemented in, or as part of, an ultrasonic detector,such as the ultrasonic detector 106. This latter implementation producesa completely self-contained composite laminate characterization systemthat both scans a composite laminate sample and analyze its own scandata directly (i.e., no separate analysis system is needed).

Referring still to FIG. 1 , the laminate characterization system 100 isuseful for, and has applicability in, a large number of industrial andmanufacturing environments. One example where the laminatecharacterization system 100 is particularly beneficial is in situationwhere information from the OEM or from an after-market modification onthe composite stack is limited or perhaps unknown and the as-fabricatedstructural characteristics (e.g., stiffness and/or failure envelope)must be obtained without destructive testing. Another application is inthe field of quality control, for example, to compare the as-fabricatedlaminate behavior with the as-designed characteristics. Yet another areawhere the laminate characterization system is useful is in ultrasonicdetector design and/or selection for a known class of compositelaminates.

FIG. 2 illustrates the exemplary laminate characterization system 100 ofFIG. 1 in more detail, including some of the components that are used inthe system. Such a system 100 is a conventional workstation, desktop, orlaptop computer, or it is more like a mobile or handheld system, or itis a custom-developed system, such as an ultrasonic detector thatincludes the additional capability discussed herein. In the exampleshown, the laminate characterization system 100 includes a bus 200 orother communication mechanism for transferring information within thelaminate characterization system 100, and a CPU 202 coupled with the bus200 for processing the information. The laminate characterization system100 also includes a main memory 204, such as a random access memory(RAM) or other dynamic storage device coupled to the bus 200 for storingcomputer-readable instructions to be executed by the CPU 202. The mainmemory 204 is also used for storing temporary variables or otherintermediate information during execution of the instructions to beexecuted by the CPU 202. The laminate characterization system 100further includes a read-only memory (ROM) 206 or other static storagedevice coupled to the bus 200 for storing static information andinstructions for the CPU 202. A computer-readable storage device 208,such as a Flash drive or magnetic disk, is coupled to the bus 200 forstoring information and instructions for the CPU 202.

The term “computer-readable instructions” as used above refers to anyinstructions that are performed by the CPU 202 and/or other components.Similarly, the term “computer-readable medium” refers to any storagemedium used to store the computer-readable instructions. Such a mediumtakes many forms, including, but not limited to, non-volatile media,volatile media, and transmission media. Non-volatile media include, forexample, optical or magnetic disks, such as the storage device 208.Volatile media include dynamic memory, such as main memory 204.Transmission media include coaxial cables, copper wire and fiber optics,including wires of the bus 200. Transmission itself takes the form ofelectromagnetic, acoustic or light waves, such as those generated duringradio frequency (RF) and infrared (IR) data communications. Common formsof computer-readable media include, for example, a floppy disk, aflexible disk, hard disk, magnetic tape, other magnetic medium, a CDROM, DVD, other optical medium, a RAM, a PROM, an EPROM, a FLASH EPROM,other memory chip or cartridge, or any other medium from which acomputer reads.

The CPU 202 is coupled via the bus 200 to a display 210 for displayinginformation to a user. One or more input devices 212, includingalphanumeric and other keyboards, mouse, trackball, cursor directionkeys, and so forth, is coupled to the bus 200 for communicatinginformation and command selections to the CPU 202. A communicationsinterface 214 is provided for allowing the laminate characterizationsystem 100 to communicate with an external system or network.

In accordance with the disclosed embodiments, a laminatecharacterization application 216, or rather the computer-readableinstructions therefor, also resides on or be downloaded to the storagedevice 208. The laminate characterization application substantiallyembodies the concepts and principles of the earlier-mentioned laminatecharacterization application in the form of a specific softwareapplication developed using a particular programming language. Such asoftware application is then executed by the CPU 202 and/or othercomponents of the laminate characterization system 100 to analyze andcharacterize the structure of composite laminate materials, as will bediscussed further herein.

The programming language used to implement the laminate characterizationapplication 216 includes any suitable programming language known tothose having ordinary skill in the art, and the application is able tobe developed in any suitable application development environment knownto those having ordinary skill in the art. Examples of programminglanguages include MATLAB (from The MathWorks, Inc.) and LabVIEW (fromNational Instruments, Inc.), as well as C, C++, FORTRAN, and VisualBasic and the like.

Referring now to FIG. 3 , in one embodiment, the laminatecharacterization application 216 comprises a number of discretefunctional components, including a data acquisition component 300, a plydetection component 302, and a failure prediction component 304.Although not specifically shown, a graphical user interface (GUI) isalso present in some embodiments for allowing users to interact with andprovide input to one or more of the functional components. Otherfunctional components are able to be part of the laminatecharacterization application 216 without departing from the scope of thedisclosed embodiments. Note that although the functional components ofthe laminate characterization application 216 have been depicted asindividual components in FIG. 3 , those having ordinary skill in the artwill understand that two or more of these components are able to becombined into a single component, and that any individual component isable to be divided into several constituent components, or omittedaltogether, without departing from the scope of the disclosedembodiments.

In general operation, the data acquisition component 300 functions toreceive and process scan data into the laminate characterizationapplication 216 for characterization and testing of a given compositelaminate sample. This scan data comes from an ultrasonic imagesimulator, as described further below, or from a real ultrasonicdetector. In either case, the data acquisition component 300 alsoprocesses the scan data in some embodiments, including scrubbing andcleaning the data as needed of any extraneous or unwanted input, such asnoise and artifacts from the ultrasonic detector. In some embodiments,instead of a single pulse for a given location, several pulses (e.g., 5to 20) of the same location are taken, then the signals are averagedtogether.

An example of an ultrasonic image simulator that is used with thelaminate characterization application 216 in some embodiments isdepicted in FIG. 4 . As is seen, the ultrasonic image simulator 400,like the laminate characterization application 216, is composed ofseveral functional components, including an ultrasonic detectorsimulator 402 and a composite geometry simulator 404. As before, otherfunctional components are also able to be part of the ultrasonic imagesimulator 400 without departing from the scope of the disclosedembodiments. The composite material data needed to conduct thesimulation is provided from one or more readily available compositematerial database 406 or other sources. In general, the ultrasonicdetector simulator 402 operates to emulate real ultrasonic responsesignals, while the composite geometry simulator 404 generates thegeometries of a composite laminate sample. These two functionalcomponents operate together to produce ultrasonic scans, or rather thedata representing the scans, of the composite laminate samples.

In some embodiments, the ultrasonic image simulator 400 is configured tosimulate ultrasonic response signal from a C-scan or C-scan equivalentdetector in pulse-echo mode (though it is also possible for theultrasonic image simulator 400 to operate in through-transmission mode).The ultrasonic image simulator 400 accomplishes this by using standardor known theories for 1-dimensional sound wave propagation within anattenuating medium (see, e.g., Schmerr, L. W., Fundamentals ofUltrasonic Nondestructive Evaluation, 1998, Plenum Press; Lonne et al.,Review of Quantitative Nondestructive Evaluation, 2004, pp. 875-882). Anacoustic pulse within an attenuating medium will generate a refractionand reflection wave whenever there exists a material boundary, such asoccurs within the CFRP as the wave passes between the resin rich regionsand the impregnated carbon fibers. In accordance with the disclosedembodiments, the ultrasonic image simulator 400 generates ultrasonicC-scan images for various industrial ply types over a wide range ofdefects, including misalignments during layup, voids due tomanufacturing limitations, and intentionally fabricated holes such asfor mounting the component.

The scan data is then analyzed by the ply detection component 302. Insome embodiments, the ply detection component 302 does this by analyzingeach time integration point (where time is directly correlated to depthwithin the laminate) and using an appropriate mathematical imagereconstruction mechanism to capture the primary directions of the ply.In some embodiments, the Radon transform, Hough transform, anEigensystem analysis, Fast Fourier transform, and the like are used todetermine the fiber principal directions and thus the fiber orientationdirections of a given laminate. Each C-scan is integrated in X and Ydirections to produce a bulk signal for a given depth in the lamina (asshown in the examples in FIGS. 8A & 8B). The overall lamina thickness isdetermined by the time of flight of the signal to the back wall of thelamina. Individual ply thickness is determined by the time of flightbetween the individual peaks in the bulk signal. The eigenvectorsgenerally correspond to the alignment direction of the ply at a givendepth, and the ratio of the transform peaks generally correspond towhether the ply is unidirectional (i.e., this is analogous to when thefirst eigenvalue is much higher than the second eigenvalue, and couldalso be found using classical eigenvalue analysis) or is a woven fabric(i.e., when the transform peaks are of similar magnitude) where theratio implies the degree of warp within an individual ply.

In some embodiments, the stack thicknesses and ply orientation is thenused with the results from the ply detection component 302 along withthe constitutive material properties of the matrix and reinforcement toobtain the structural stiffness tensor using known laminate theories(see, e.g., R. M. Jones, Mechanics of Composite Materials, SecondEdition, New York, Taylor and Francis, 1999 (“Jones”), where in thepresent configuration the lamina stiffness is obtained using thewell-known Tandon-Weng theory (see Tandon, G.P. and G.J. Weng, TheEffect of Aspect Ratio of Inclusions on the Elastic Properties ofUnidirectionally Aligned Composites, Polymer Composites, 5(4):327-333,1984 (“Tandon-Weng”)) with the closed form solution implied by Tuckerand Liang (see Tucker, C. L. and E. Liang, Stiffness Predictions forUnidirectional Short-Fiber Composites: Review and Evaluation, CompositesScience and Technology, 59:655-671, 1999 (“Tucker and Liang”)) forunidirectional laminas. There exist a host of many alternativemicromechanical methods to predict the ply stiffness response once theunderlying constitutive ply makeup is understood, and the above are justunderstood to be one of the better alternative schemes. It is of coursepossible and known to analyze the stack thicknesses and fiberorientation for hybrid and non-hybrid woven fibers as well asunidirectional fibers. See, e.g., Scida et al., Elastic behaviorprediction of hybrid and non-hybridw oven composite, Comp. Science andTechnology, 1997, 57:1727-1740 (“Scida”).

If the manufacture-supplied stiffness (“C”) and/or compliance (“S”)tensors (one is the inverse of the other) is provided, the stiffness ofa unidirectional laminate in the principal material directions is foundfrom the constitutive materials. On the other hand, if a unidirectionalply is assumed, only the properties of the constitutive materials areneeded, such as the isotropic stiffness of the epoxy and thetransversely isotropic stiffness tensor of the carbon fibers. Thesevalues are used as taught in Tandon-Weng, to return the effectivestiffness of the lamina using a unidirectional plane stressapproximation. Another option is the outdated, but industrially-acceptedmethod discussed in Halpin, J. C. and J. L. Kardos., The Halpin-TsaiEquations: A Review, Polymer Engineering and Science, 16(5):344-352,1976 (“Halpin-Tsai”), or as discussed in Tucker and Liang, the moreaccurate approach of Mori, T. and K. Tanaka, Average Stress in Matrixand Average Elastic Energy of Materials with Misfitting Inclusions, ActaMetallurgica, 21:571-574, 1973 (“Mori-Tanaka”), of using the approachoutlined in Tandon-Weng. Both approaches require knowledge of theYoung's modulus and Poisson Ratio of the fiber, E_(f) and v_(f),respectively, and the matrix, E_(m) and v_(m). In addition, they requirethe volume fraction of fibers v_(f) and the effective aspect ratio ofthe individual fibers within the tows a_(r). Completion of thesecalculations return the stiffness and compliance tensors, along with thedesired planar Young and Shear Moduli and Poisson's Ratios, E₁₁, E₂₂,G₁₂, G₂₃, v₁₂, and v₂₃, which could alternatively be obtained directlyfrom the components of S. This tensor is then rotated into the compositecoordinates using standard tensor rotations. Once the underlyingstiffness tensor for a given lamina is understood, any of a variety ofclassical laminate theories are able to be used to predict thefabricated composite's stiffness components. See, e.g., Barb ero, E. J.,Introduction to Composite Materials Design, Second Edition, 2011(“Barbero”); Jones.

The individual lamina failure envelopes are thereafter used by thefailure prediction component 304 to generate a failure envelope for thecomposite laminate, once the ply stiffness is known and the materialfailure parameters of the matrix and fiber are known. This isaccomplished using any of the industrially-accepted techniques, such asthe Tsai-Wu failure criteria. See, e.g., Tsai, S. W., and Wu, E. M., Ageneral theory of strength for anisotropic materials, J. Compos. Mater.,5, pp. 58-80 1971 (“Tsai-Wu”); see also Jones or Barbero. In general,the Tsai-Wu criteria is used to generate the failure envelope of thelamina, and that information is then used with ply failure theories topredict the failure of the laminate. Unlike traditional approaches thatassume the load is planar, the failure prediction component 304 handlesa generalized 6-dimensional loading condition, including 3 differentmutually orthogonal normal stresses and 3 different mutually orthogonalshearing stresses. In some embodiments, the failure envelopes of thecomposite laminates are analyzed assuming a degree of uncertainty withinthe stack, such as the ply orientation, and the probabilistic failureenvelopes are generated using a Monte-Carlo approach. See, e.g., Vo, T.and D. A. Jack, Structural Predictions of Part Performance for LaminatedComposites, 2011 ECTC Proceedings. This approach allows characterizationof a probabilistic confidence of the actual failure envelope of theas-processed composite laminate based on the uncertainties in the plydetection algorithm.

The above embodiments are particularly useful for modifiers of compositestructures who do not have direct access to original manufacturing,operations, maintenance and repair information. QA personnel who providevarious composite structure quality assurance services where the OEMinformation is typically available also find the disclosed laminatecharacterization system beneficial. In general, the laminatecharacterization system helps provide: detailed comparison ofas-manufactured to as-designed composite structures; detailedcharacterization of initial state load carrying capability; detailedcharacterization of use or age related intra-lamina issues; reduction orelimination of so-called “coupon” or sample testing requirements;reduction in margins of safety in design leading to reduced weight forcomposite end items; the ability to independently and non-destructivelyvalidate composite material stack up without OEM or MRO design ormanufacturing records; and the ability to certify a modified compositestructure or structural repair without OEM design or load informationusing an equivalent strength methodology.

Detector Considerations

With respect to the types of detectors used, the major parameters thataffect an ultrasonic pulse within a medium are the speed of sound withina particular material and the optical impedance of the material, definedas the material density multiplied by the local speed of sound. Also ofinterest is the type of wave generated by the detector. There aretypically two types of waves of interest in NDT, plane waves and shearwaves. Both types will be present within any given material, butdepending on the detector configuration one or both types is captured.Some detectors use a fluidic interface between the detector and thematerial being sampled, and thus due to the inability of shear waves topass through a fluidic media, these detectors are best used in apulse-wave dominated configuration using a pulse-echo method where asingle transducer is used as both a transmitter and a receiver or in athrough transmission mode where one transducer is placed on each side ofthe object of interest. The signal will be scattered whenever a changein the acoustic impedance (often defined loosely as the material densitytimes speed of sound) changes within a structure, thus whenever a beampasses between the matrix and a tow, a signal will be scattered and theobjective of NDT is to capture and interpret this signal.

A third parameter of interest is the attenuation of the signal's poweras a function of frequency. In graphite composites, for example, thespeed of sound is in a range near 3 mm/μs. At 10 MHz, the cycle time fora single wavelength is 0.1 μs or 100 ns and the corresponding wavelengthis 0.3 mm. Thus, the cycle time for an individual wavelength must beless than or equal to the sensor gate (integration) time to avoid errorsin detected signal amplitude due to partial wave integrations.

Pulse-wave detectors function by sending out a pulse and waiting for theechoes from the changing impedance of the target material. The variablesof interest for these detectors are the ‘z-start’ and ‘z-gate’ times.The z-start time is the time at which the detector starts to detect andintegrate the echoed signal in the z-axis (equivalent to the depth), andthe z-gate time is the period during which the detector is integratingor “listening” to the echoed signal. These times correspond,respectively, to the initial depth and thickness of the lamina beingtest. For example, using a 10 MHz signal in a CFRP laminate, a z-startof 0 and a z-gate of 1.0 μs corresponds to an image that starts at thelaminate's surface and produces an echoed signal from the first 3 mm ofmaterial. Sub-microsecond z-gates and frequencies greater than 10 MHzare therefore necessary to detect fiber tows with typical thicknesses of0.214 mm. A 20 MHz detector with a 50 ns z-gate allows a theoreticalresolution of 0.145 mm.

The detector resolution is also a function of the ultrasonic image'spixel resolution, with each pixel representing the smallest discretespatial location that is able to be assessed for a given compositelaminate sample. A typical pixel is about 0.21 mm in the X and Ydirections (i.e., length and width) for high end commercially availablecharacterization systems, corresponding to a signal having about a 20MHz frequency. The choice of frequency is a trade-off between spatialresolution of the image and imaging depth. Lower frequencies produceless resolution, but penetrate deeper into a sample. Higher frequencieshave a smaller wavelength and thus are capable of reflecting orscattering from smaller structures, but have a larger attenuationcoefficient and thus the signal is more readily absorbed by the plies,limiting the penetration depth of the signal.

Following is a more detailed description of some of the methods,assumptions, and procedures used with the laminate characterizationapplication 216 in accordance with some embodiments, beginning withoperation of the ultrasonic image simulator 400.

Geometric Simulation

As mentioned with respect to FIG. 4 , in some embodiments, theultrasonic image simulator 400 includes a composite geometry simulator404 configured to provide the geometry of a laminate. The compositegeometry simulator 404 takes as inputs the areal density, fiber towwidth, and warp percentage to establish the spacing of the fibers for agiven lamina in the X and Y directions (i.e., length and width). Thisinformation is provided, for example, from a composite material database406 and the like and includes the ply material thickness. The compositegeometry simulator 404 then builds a 3-dimensional matrix of layers byorienting individual fibers to the layer angle of orientation input bythe user. Because fiber placement is usually not rigorously controlledto sub-tow width, the composite geometry simulator 404 randomly adjuststhe starting fiber position for each layer (i.e., so the fibers will nottypically lay perfectly on top of one another in the X and Y directionseven for layers having the same orientation). In addition, depending onmanufacturing technique, fiber orientation is not perfect, and thecomposite geometry simulator 404 is configured to simulate suchimperfection. Specifically, the composite geometry simulator 404simulates fiber orientations from the following processes: machine layup(almost no orientation variability from planned), machine assisted layup(about 0.8 degrees standard deviation from planned), and hand layup(about 4 degrees standard deviation from planned).

In addition, the composite geometry simulator 404 is also configured tosimulate voids between the individual layers of the laminate. In theassembly of individual layers, air becomes trapped, leading to an epoxyvoid between layers. In real applications, these voids effectivelyabsorb the ultrasonic pulse so that the layers below these voids are notdetected. Typical values of voids are 1% to 2% by volume of thecomposite laminate. The geometry simulator allows for the introductionof these voids and simulates them randomly between layers. The voidshave material properties of air and are made ellipsoid in shape and varyrandomly in size, X, Y and interlayer position. Void volumes are userselectable between 0%, 1%, 1.5%, 2%, or more by volume.

The composite geometry simulator 404 also has the ability to introducedrilled holes of various diameters and X and Y positions. These also aresimulated with material properties of air, but unlike the voids, thesecontinue through all layers.

Finally, the composite geometry simulator 404 allows the user tosimulate a rectangular insert of a different material property betweenselected layers. In practice, these inserts are typically made of Teflonor similar material. The rectangular area is simulated by assigning thedesired materials density and associated speed of sound in the geometrymatrix where desired. The purpose of this rectangular insert is tosimulate a large scale “flaw” in the material that, unlike the voidsdiscussed above, does not cause an ultrasonic signal to be completelyabsorbed by the flaw, so continued detection beneath this material ispossible. The insert is then used as a way to properly calibrate X, Yand Z resolution.

Ultrasonic Detector Simulation

In general, the ultrasonic detector simulator 402, which is developedusing MATLAB or other similar programming language, makes use ofwell-known NDT fundamentals (see, e.g., Schmerr, L. W., Fundamentals ofUltrasonic Nondestructive Evaluation, Plenum Press, 1998) (“Schmerr”).This ultrasonic detector simulator 402 is for a general multidimensionalsignal with both plane and shear waves, or it is simplified for a 1-Dpulse-echo assumption (no shear waves). Such an ultrasonic detectorsimulator 402 is then be used to provide a simulation of an ultrasonicC-scan for a composite laminate.

In the present embodiment, each discrete spatial location (i.e., pixel)in the ultrasonic C-scan, the ultrasonic detector simulator 402 usesknowledge of the location of the transition between each layer as wellas the material properties (e.g., speed of sound, material density,etc.) of the layer from the geometric simulator. The governingdifferential equations of an acoustic medium are then solved numericallyto simulate an ultrasonic wave translating within the part at anindividual spatial location. The resulting intensity solution as afunction of time is typically stored in an array for each spatiallocation in the simulated scan, such that each spatial location isassociated with a separate array.

The ultrasonic detector simulator 402 also uses inputs for the waveintensity at the initial surface. Using an Ordinary DifferentialEquation (ODE) solver, the wave front is computed as a function of time.Although an ODE solver is not needed to determine how long it takes fora wave to pass between the layers, the ODE solver has an additionalbenefit in that signal attenuation is readily incorporated. The fullanalysis for the wave propagation is not described in detail here, as itis readily obtained from standard NDT textbooks, including Schmerr.

Care should be taken when the wave enters a boundary andreflects/refracts, as the equations that capture reflection/refractionbehavior between layer transitions involving pure epoxy and epoxy/fiberlayers (see, e.g., Equations (6.157)-(6.168) of Schmerr) for an incidentp-wave (a.k.a., the elastic wave of the pressure wave, often attributedto compression effects) and the s-wave (a.k.a. the shear wave or thesecondary wave, often attributed to the change in shape of an object)assume that the interface between layers is represented by amathematically continuous contact. This is appropriate when there isperfect (or near perfect) bonding between the fiber and the resin.

The intensity of each wave is a function of the amplitude of thepressure pulse, density of the material, the speed of sound of thematerial, and attenuation behavior of the medium. Using Equations(6.7)-(6.16) of Schmerr, the ultrasonic detector simulator 402 is ableto properly account for the intensity of every individual ray within thelaminate.

In some of the lower quality embodiments, the ultrasonic detectorsimulator 402 assumes an ideal material where there is no signalattenuation within the medium, although this is not realistic for higherfrequencies (e.g., greater than 10 MHz), as it is known that as thefrequency of the incident signal increases, polymeric materials tend todamp out the signal. An additional feature of the ultrasonic detectorsimulator 402 is the ability to tailor the intensity cutoff, thusmimicking the physical threshold of the physical detector. In general,the more layers exist within a laminate, the more independent rays willexist within the composite due to the bounce-between of the rays betweenlayers. The more a ray bounces between layers and splits into areflected and refracted wave, the weaker the signal becomes.

The current ultrasonic detector simulator 402 also performspost-processing to analyze the dependence of the returned signal outputfor both pulse duration, Δt_(Power Pulse), and z-gate width,Δt_(z-gate). For example, if the detector pulse were left on too long orhad a long ring time after the initial pulse, it is impossible todistinguish the returned signal from individual layers. The z-gate widthis also a significant consideration as a z-gate value that is too largewill capture the return signal from multiple layers. The smaller thez-gate, the greater the accuracy of the detector, but this comes at areduction in the total intensity and thus could impose on thresholdlower limits.

In some embodiments, the ultrasonic detector simulator 402 simulatescertain physical detectors, which do not return the signal as a functionof time. Instead, the ultrasonic detector simulator 402 returns theaverage intensity of the signal as a function of time through a formsimilar to:

$\begin{matrix}{{\overset{\_}{I}\left( {t_{z - {gate}{start}},{\Delta t_{z - {gate}}}} \right)} \equiv {\frac{1}{\Delta t_{z - {gate}}}{\int_{t_{z - {gate}{start}}}^{t_{z - {gate}{start}} + {\Delta t_{z - {gate}}}}{{I\left( {t,{\Delta t_{{Power}{Pulse}}}} \right)}{dt}}}}} & (1)\end{matrix}$

where Ī(t_(z-gate start), Δt_(z-gate)) is the average intensity at agiven start time and will depend on the entered z-gate width. This valueis often reported at a certain depth for a homogeneous material, butthis description will be somewhat ambiguous as the “depth” of a signalis a function of the material impedance (density multiplied by the speedof sound). In the case of a composite laminate, this cannot be knowna-priori as the material in question has a spatially varying materialmake-up and even the choice of matrix hardener have impact significantlythe resulting speed of sound of the material.

Graphical User Interface

FIG. 5 illustrates an example of a graphical user interface (GUI) thatis provided with the ultrasonic detector simulator 402. As is seen, insome embodiments, the user is provided with the option to select type ofdetector, which will establish the resolution of the ultrasonic scan tobe output. The highest resolution provided by the simulated detector has0.1 mm resolution in the X and Y axes and single-lamina resolution inthe Z direction. Examples of available selections for “real” detectorsinclude the Imperium 1-600 detector with 0.21 mm resolution in the X andY direction and Z resolution controlled by various frequency ranges andz-gate timing from 2.7 MHz-20 MHz.

Another user input choice is “manual” or “material database.” If“manual” is selected, then the user inputs the individual parametersmanually. Selection of “material database” allows a user to select froma database of materials listing the available composite material data.The user then selects a material and the data therefor will beautomatically loaded into the ultrasonic detector simulator 402.

An example of the data contained in the material database is provided inTable 1 below for various plies in several common composite laminates.These configurations were obtained from various handbooks andmanufacturers databases, and are provided as typical examples oflaminate stacks. Other sources include the MIL-17 handbook series“Composite Materials Handbook,” which contains the effective stiffnesstensor data for a wide variety of military standard laminas.

TABLE 1 Material Properties Aereal Warp Tow Fiber Ply Num of NameDensity % Width Volume Thickness Plys Cytec 7714A T650-35 195 0.5 0.3760.54 0.2 18 Cytec 7714A M461 195 0.95 0.394 0.54 0.2156 15 Cytec 7714ASHST-35 380 0.5 0.75 0.57 0.429 10 FiberCote T300 SHS 6K 380 0.5 0.750.57 0.429 10 Cytec 7740 T650-35-35-PW-195-4 195 0.5 0.376 0.54 0.2 18

Once a material is loaded, the user selects the z-gate width and z-gatestart for output display. In perfect detector mode, this selection isaccomplished in layer units and the z-gate step is in single layers. Insimulated detector modes, this input is in millimeter for all threevalues and z-gate width is limited to unit wavelengths which is afunction of the selected detector frequency.

The user then selects assembly methods, flaw sizes, holes and holepatterns, and the Teflon insert. Once all of these selections are made,the ultrasonic detector simulator 402 generates a series of C-scanimages at different depths throughout the simulated laminate anddisplays the result. The user then views the laminate at various depthsby selecting the appropriate layer. The user also selects differentz-gate widths and step sizes to produce an updated simulation.Simulations of different flaw sizes and detector types, or changes inmaterial selections, are also updated and recalculated. Once theultrasonic detector simulator 402 has produced the simulated C-scans,the results are saved for subsequent processing.

FIG. 6 illustrates the operation of the ultrasonic image simulator 400described above in the form of a flowchart 600. As is seen, operation ofthe ultrasonic image simulator 400 begins, including of the geometry ofthe composite laminate being simulated at block 602 a, including spatialinformation for fiber tows and sound properties for fiber and resin, andthe like, and defining the properties of the ultrasonic emitter/detectorbeing simulated, including signal intensity, sensitivity, frequency,waveform length, waveform shape, and the like, at block 602 b is. Atblock 604, for every spatial position (i.e., pixel) on the compositelaminate, the ultrasonic image simulator 400 solves the equations oftransmission for the intensity observed by a detector.

Then, at block 606, the ultrasonic image simulator 400 numericallysolves (e.g., using ODE techniques) spatial and temporal form of wavetransmission equations of motion for signal intensity spectrum as afunction of time. These equations are found, for example, in Lonne, S.,A. Lhemery, P. Calmon, S. Biwa, and F. Thevenot, Modeling of UltrasonicAttenuation in Unidirectional Fiber Reinforced Composites CombiningMultiple-Scattering and Viscoelastic Losses, in review of QuantitativeNondestructive Evaluation, editors D.O. Thompson and D.E. Chimenti, pp.875-882, published by American Institute of Physics, 2004 (“Lonne”).Specifically, Lonne provided plots that suggested an attenuationcharacteristic within a composite laminate. A mathematical form is usedfor attenuation, as follows, Attn=10^(−(af+b)Δx/20), where f frequency,a and b are experimentally observed coefficients, and Δx is the distancecovered by a pulse in a given time of interest.

At block 608, the ultrasonic image simulator 400 retains the intensitysplit as a pulse passes between layers and lends itself to a reflectionand refraction pulse. At block 610, from the 1-dimensional solution, theultrasonic image simulator 400 retains surface return intensity (bothfront and back surface for, respectively, pulse-echo and throughtransmission), as this represents the A-scan signal observed by adetector. Once the above operations have been performed for everyspatial position (i.e., pixel) on the composite laminate, then at block612, the ultrasonic image simulator 400 compiles the A-scans from eachspatial location into a spatially resolved image of the returnedintensity at a moment in time. These compiled A-scans results comprisethe C-scan images that are subsequently provided to the ply detectioncomponent 302 for further analysis (see FIG. 7 ).

Ply Detection Process

Continuing with embodiments of the invention, data representing theC-scan images of the composite laminate, whether from an actual detectoror simulated as described above, is provided to the ply detectioncomponent 302 for further processing. Actual detector data, of course,means the analysis is being performed on a real composite laminatesample, whereas simulated data is more beneficial for purposes oftesting and fine tuning the operation of the ply detection component302.

FIG. 7 generally illustrates the operation of the ply detectioncomponent 302 in the form of a flowchart 700, beginning with block 702,where A-scans with 10 ns or less timing and less than 0.25 mm spacing inthe X and Y direction are acquired, either from a real detector or froman ultrasonic simulator (see FIG. 6 .), for a composite laminate. Theply detection component 302 uses these A-scans to generate C-scan sliceswith 10 ns steps or increments and 10 ns z-gates at block 704 byintegrating the A scan amplitude data over the timing gate relative tothe initiation of the reflected signal which signifies the front face ofthe laminate. In this way, the timing from all A scans represents thesame depth within the laminate producing a slice across the laminate ata known depth. At block 706, the ply detection component 302 processesthe C-scan slices using filters, thresholding and morphologicalfeatures. These filters include normalizing the signal and applyingvarious top and bottom thresholds to remove noise or saturated signalswhich cause inaccuracies in the image transforms. When identifying weavetypes, various linear and 2-dimensional morphological filters are usedto pass or remove signals prior to final image transforms. At block 708,the ply detection component 302 uses the bulk C-scan amplitude signal asshown in FIG. 8 to determine the number of plies, the width per ply, andthe total laminate thickness using bulk image properties.

At block 710, the ply detection component 302 again generates C-scanslices using the A-scans, except that these C-scan slices are about athird of the individual ply thickness from the front wall to 1.3 timesthe laminate stack thickness. This is done to insure a given slicerepresents the “center” of a ply and is therefore not compromised by theply above or the ply below. These C-scan slices are again processedusing filters, thresholding, and linear morphological features at block712. At block 714, the ply detection component 302 applies one ofseveral possible 2-dimensional transforms and thresholding to the C-scanslices to determine their primary and secondary orientations. Primaryorientations are the highest resultant transform signal and secondaryorientations are the second highest transform signal from the filteredresults as shown in FIG. 9 for a simulated weave. Examples of2-dimensional transforms that are used include the well-known Radontransform, Hough transform, Eigensystem analysis, the Fast FourierTransform (FFT), and the like.

Once the primary and secondary orientations are determined, as at block716, the ply detection component 302 uses the orientations to determinewhether each C-scan slice is a weave or unidirectional. Thisdetermination is performed by first filtering the orientation data toremove outliers, and overlapping plies, at block 718. At block 720, theply detection component 302 uses the previously determined ply thicknessto apply a timing mask corresponding to the predicated steps for eachindividual ply. The ply detection component 302 thereafter usesstatistical techniques to determine the most likely ply orientation bylooking at a histogram of most likely ply angles for the stepsassociated with a given ply mask and type (e.g., weave, unidirectional,etc.) from the remaining data, at block 722. By statistically buildingup data from all slices in a given ply, a most probable determination ismade. With the information on the number of plies, ply thickness, andply orientation now available, a failure envelope is determined for thecomposite laminate.

Operation of the ply detection component 302 discussed above was studiedover a range of possible ply examples. For these examples, a narrowz-step size (10 ns) and a narrow z-gate (100 ns) was used to createapproximately 15 images per ply for thin plies and approximately 30images per ply for thick plies. These numbers provided sufficientstatistical data to determine a final ply orientation. The studyproduced an output of the bulk image properties as a function of z-stepsize, similar to that shown in FIGS. 8A & 8B. In the figure, the plythickness output for a 10-ply stack is shown in the plot on the left,where the vertical axis represents C-scan amplitude and the horizontalaxis represents the number of z-steps being made. The result is asmoothed plot of the bulk response showing peaks at several steps, withthe last step being the back wall. The plot on the right shows thenumber of plies as determined by the number of first derivative zerocrossings, plus 1 zero crossing assumed for the first layer.

Once the number of plies is determined and the total thickness isdetermined, the number of z-steps being made per ply is determined. Thenumber of z-steps per ply and initial z-step showing signal (wherez-gate plus z-step crosses the boundary from ply 1 to ply 2) allows fora mask to be used to isolate the plies. In the example shown in FIGS. 8A& 8B, this is about 17 z-steps per ply. Ply number 2 information isprovided between z-steps 8 and 24. Ply number 3 information is betweenz-steps 25 and 41, and so forth.

FIGS. 9A & 9B reflect an example of the ply orientation for the exampleof FIGS. 8A & 8B, corresponding to ply number 1 (zero degreesorientation) and ply number 2 (10 degrees orientation). In this example,the plot in FIG. 9A, with the vertical axis representing Radon amplitudeand the horizontal axis representing orientation in degrees, was derivedusing a modified Radon function, where various filters were applied withan orientation from 0 to 180 degrees for detection. In that plot, theright peak (Peak 1, at about 100 degrees) represents the primaryorientation and the left peak (Peak 2, at about 10 degrees), representsthe second reorientation. The image in FIG. 9B is the C-scan output ofthe ultrasonic detector simulator 402 corresponding to the Radon imagein FIG. 9A. As is seen, the plot in FIG. 9A shows the primary andsecondary fiber orientation peaks for each z-step. From FIG. 9A, anorientation is determined. If the two peaks are roughly 90 degrees outof phase with each other and of roughly the same magnitude, adetermination is made that this represents a weave. The z-step hereindicates a weave fiber pattern because, although a unidirectional fibershows two peaks, the primary and secondary peaks are usually on top ofeach other. The ply type (weave or unidirectional) is thereforedetermined automatically in some embodiments.

FIGS. 10A & 10B show an example of a scatterplot (left-hand plot) ofdetermined primary and secondary orientations from z-steps 8 through 24.This scatterplot shows either a 10 degree or 100 degree orientation,with the horizontal axis representing z-step number, and the verticalaxis representing angles in degrees, and circles represent the primaryorientation and squares represent the secondary orientation. Using thehistogram approach on the primary and secondary peaks, the right plotshows the output determination for ply number 2—a weave with primaryorientation 10 degrees and secondary orientation 100 degrees—where thehorizontal axis is angles in degrees, and the vertical axis is the countcorresponding to the primary and secondary angles from each step in FIG.10A).

A filter is applied to determine the orientations that represent realsignals versus noise, as shown in the illustrative examples of FIGS. 11A& 11B and FIGS. 12A & 12B. In these figures, the left-hand plots aresimilar to the plot shown in FIGS. 10A & 10B, while the right-hand plotshave the z-steps along the horizontal axis and ply orientation anglesalong the vertical axis. FIGS. 11A & 11B are the unfiltered histogramfor a unidirectional case with possible ply orientations 0, 30, 60, 90,120, and 150 degrees (for a 0 to 180 degree orientation), and FIGS. 12A& 12B are the filtered histogram showing the determined possibleorientations.

The final results for the ply detections are presented, for example, inthe form of a spreadsheet similar to the one shown in FIGS. 13A & 13B,which is being provided for illustrative purposes only. The examplespreadsheet shows some of the relevant ply information and a graphicshowing the detected ply orientation as a function of z-step. In thisexample, the spreadsheet includes the ply number (first column fromleft), the calculated ply orientation (second column), actualorientation (third column), and ply type (e.g., unidirectional, weave,etc.) (fourth column). The fifth and six columns show the averagecomputed thickness and average actual thickness for the plies,respectively. These results are then provided to the failure predictioncomponent 304 to be used for probabilistic failure envelopedetermination.

The foregoing failure prediction operation is set forth in FIG. 14 interms of a flow chart 1400. Beginning at block 1402, the failureprediction component 304 receives the ply orientation after step 722 ofFIG. 7 , ply type and thickness from the ply detection component 302.Any uncertainty or variability as a function of the detector type isalso inputted or signed at this time in the form of the stochasticdistribution or in terms of the mean and variance of the input. At block1404, the material properties (either the fiber and matrix moduli,failure parameters, packing density, and fabric type, or theexperimentally obtained or manufacture supplied lamina stiffness tensorand failure parameters) for the composite laminate sample is defined orotherwise provided to the failure prediction component 304 along withtheir uncertainties.

Thereafter, the failure protection component randomly samples a set ofproperties for each layer of each probabilistic parameter, whichincludes orientation, fiber stiffness tensor, matrix stiffness tensor,ply thickness, ply type (weave type or unidirectional), fiber volumefraction, porosity, and so forth, at block 1406. At block 1408, thefailure prediction component 304 generates the bulk laminate stiffnessmatrix from the constitutive materials' properties. This is done usingwell-known laminate theory (see, e.g., Jones) and is probabilistic innature. The failure prediction component 304 then selects a planarloading scenario and linearly increase each load variable until failureoccurs, at block 1410. Possible failure theories that are used hereinclude Tsai-Wu and Tsai-Hill, as both were discussed in K-S Liu, S. W.Tsai, A Progressive Quadratic failure criterion for nonlinear analysisof composite laminates subjected to biaxial loading, Composites Scienceand Technology, 1998 58:1107-1124 (“Liu and Tsai”); A. Puck, H.Schurmann, Failure analysis of frp laminates by means of physicallybased phenomenological model, Composites Science and Technology,58(7),1045-1067 (“Puck and Schurmann”); and the like.

Once failure is identified for a given loading scenario, the failureprediction component 304 repeats the process for each possible planarloading scenario for full failure envelope at block 1412. At block 1414,the failure prediction component 304 returns to block 1406 and thisprocess is repeated for a sufficient number of samples to identify asmooth form for the probabilistic failure curve. If a smoothrepresentation of the probabilistic failure curve is obtained, then theresults are analyzed at block 1416. The analysis involves, from aquality control perspective, using use the envelope to quantify theprobability of failure for an in-service part under a known (eitherdeterministic or probabilistic) load, at block 1418. Alternatively, atblock 1420, the analysis involves, from a design perspective, expandingthe failure curve sufficiently to encompass an acceptable percentage offailure loads for a replacement or supplemental part.

Such an arrangement is particularly useful for modifiers of compositestructures who do not have direct access to original manufacturing,operations, maintenance and repair information. QA personnel who providevarious composite structure quality assurance services where the OEMinformation is typically available also find the disclosed laminatecharacterization system beneficial.

The foregoing embodiments characterize and quantify composite laminatestructures. These embodiments take a composite laminate of unknown plystack composition and sequence and determine various information aboutthe individual plies, such as ply stack, orientation, microstructure,and type. The embodiments distinguish between weave types that exhibitsimilar planar stiffness behaviors, but produce considerably differentfailure mechanisms. The information about the plies is then used toderive the laminate bulk properties from externally providedconstitutive properties of the fiber and matrix, such as extensionalstiffness, bending-extension coupling stiffness, bending stiffness, andthe like. The laminate bulk properties are then used to generate aprobabilistic failure envelope for the composite laminate. This allowsfacility owners and operators in various industries to assess, support,and maintain composite laminate structures, particularly old and agingstructures, independently of the original manufacturing failureinformation or predictions for the composite laminates structures. Theembodiments further provide the ability to perform non-destructivequality assurance to ensure, for example, that individual lamina layupwas accomplished according to design specifications, and results areused to identify a wide range of laminate properties beyond purelystructural.

In addition to the above, the concepts and principles disclosed hereinare also used to characterize and quantify curved composite laminatestructures as well as flat composite laminate structures. Such curvedcomposite laminate structures are widely used in many industries and thehigh-frequency ultrasound A-scan and C-scan techniques disclosed hereinare equally applicable to these curved composite laminate structures.

As mentioned above, carbon fiber laminates are stronger than traditionalmetals, but unlike metals their material properties are determined bythe manufacturing process. Within the manufacturing process, the plyorientation of each layer has a profound effect on the materialproperties. The disclosed embodiments take a flat laminated compositewith an unknown ply stack type and sequence and use ultrasound todetermine the ply stack sequence based on the ultrasonic signal. Fromthis information, certain material properties are calculated todetermine the structural integrity of the part or to confirm that it wasmanufactured properly. An overview of the disclosed embodiments isillustrated in FIG. 15 at 1500. As is seen, in general, the disclosedembodiments begin with a laminated composite of unknown ply stack typeand sequence, as indicated at 1502. An ultrasonic scan layer by layer isperformed on the laminate at 1504. The ply stack type and sequence arethen determined at 1506 based on the ultrasonic scans, and aprobabilistic failure envelope of the as-processed part is thendetermined at 1508.

In accordance with the disclosed embodiments, in addition to planarcarbon fiber composites, ply stack type and sequence is also determinedfor a curved carbon fiber composite using the disclosed embodiments byadding a rotational stage to the transducer control equipment. Therotational stage is used to perform a fast scan across the compositepart under test. The A-scan is then analyzed at each point to determinethe distance from the top surface of the part to the transducer plane. Avector normal to the surface is then backed out from the surface inorder to place the transducer at a predefined distance, such as thefocal length of the transducer, from the part surface, but directlyfacing the part surface. This is done by moving the transducerup-and-down along the Z-axis as well as rotating the transducer headalong a theta axis to directly face the part surface along one axis,such as when the curve is two-dimensional (e.g., a cylinder or othershape having a curve primarily in two planes with the third plane beingsubstantially constant for the increment of the measurement area) and asappropriate along other axes with other angles such as a phi axis whenthe curve is three-dimensional (e.g., a spheroid or other shape havingcurvatures in more than two dimensions). Software is used in someembodiments to automate the entire process.

FIG. 16 illustrates an exemplary implementation of the disclosedembodiments using an ultrasonic transducer 1600 to characterize andquantify curved composite laminate structures, such as a section of pipedepicted at 1602. Any suitable ultrasonic transducer 1600 known to thosehaving ordinary skill in the art capable of obtaining a C-scan is ableto be used without departing from the scope of the disclosedembodiments. In the example of FIG. 16 , the transducer 1600 has a focallength of 1.5 inches, so during the C-scan, it should be placed as closeto that distance above the part 1602 as possible.

FIG. 17A shows a view of a system 1700 for characterizing andquantifying curved composite laminate structures. The system 1700includes a transducer 1702 that is used to characterize a section ofpipe 1704, and a control system and various support structures,indicated generally at 1706. FIG. 17B shows the support structures 1706in more detail, including the electrical and motor control system 1708for the rotational stage.

To prevent creation of shear waves and thus a degradation of signalintensity, the transducer should be oriented normal to the scanningpoint, as illustrated by the vector n(x, y, z) in FIG. 18 . This isachieved by using the gradient of the known surface function of theresults produced in step 2c, discussed below.

In the above example, the coordinates (x, y, z) and the angle of theultrasonic transducer are calculated using the following equations:

N _(x) =f _(x)(x ₀ , y ₀)

N _(y) =f _(y)(x ₀ , y ₀)

N _(z)=−1

x=x ₀ +N _(x)(d+t)

y=y ₀ N _(y)(d+t)

z=z ₀ +N _(z)(d+t)

ϕ=sin ⁻¹ N _(y)(degrees)

where x₀, y₀, z₀, are points on the surface of the pipe, N_(x),N_(y),N_(z), are the different components of the Normal vector, d is thedistance in inches from the transducer tip to the center of therotational stage, t is 1.5 inches or the focal length of the transducer,and f is the angle the transducer makes with respect to the surfacenormal component N_(y).

In accordance with the disclosed embodiments, the rotational stage isadded to the high-frequency ultrasound A-scan and C-scan techniquesdisclosed herein to characterize and quantify curved composite laminatestructures, as follows.

As an initial step, Step 1, A-scan techniques are used to collect datafrom a predetermined set of grid locations on the surface of the partunder test (e.g., a pipe) with the objective being to capture the frontsurface of the part as a function of space. For best results, the entiresurface of the part should be scanned to ensure the results from Step 2bis a tight fit to the data, as discussed below.

Next, in Step 2a, MATLAB or a similar numerical computing program (e.g.,LABVIEW) is able to be used with the data from Step 1 to determine thedistance the transducer was above the part at each scan point fromStep 1. Specifically, MATLAB or similar numerical computing program isable to be used to sort through each A-scan, using a predeterminedbuffer length, and find the moment when the ultrasound signal impactedthe surface and returned to the transducer. FIG. 19 shows signalintensity versus distance in water for the A-scan of the part asproduced using, for example, MATLAB. The above result is possiblebecause when the signal comes into contact with the part, the incidentwave reflects back to the transmitter and refracts into the part. Thesignal intensity is recorded by marking the first point that is above acertain user-entered threshold, as shown by the “X” in FIG. 19 .

Then, in step 2b, the fact that the recorded point corresponds to a timevalue is used along with the speed of sound in water or another mediumin which the reading is made, which is a known quantity, to calculatethe spatial distance from the part using ultrasound technology. This isreflected in FIG. 20 , which shows the transducer distance from thesurface of the part versus the spatial distance. Lasers and othermeasurement means are used instead of ultrasound technology.

Thereafter, in Step 2c, the coordinates for the location of thetransducer are calculated using the aforementioned equations and putinto a matrix. This matrix is then sent to the motor control system ofthe rotational stage (see FIGS. 17A and 17B) to be read.

In Step 3, the coordinates from Step 2c are used to move the transducerinto the appropriate location so it is roughly 1.5 inches andperpendicular to the part surface at that point, as shown in FIG. 16 .With the above steps being done at each point, a C-scan is performed toinvestigate the ply orientation of the curved composite structure andthereby characterize and quantify the curved composite structure. In theexample of FIG. 16 , a successful 3.5×3.5 mm C-scan of the pipe section1602 was completed using the above described method and system.

It should be noted that where LABVIEW is used, the LABVIEW program needsto be modified from running on a system based on sets of scalar datastreams to a system that runs on arrays. The arrays are needed to inputthe coordinates from MATLAB into LABVIEW. As well, it should be notedthat in some implementations, the part under test only has a curvatureof four degrees or less relative to the direction vector along thetransducer in any direction to facilitate the transducer remainingperpendicular to its surface, but in other embodiments, the curvature isable to be greater and thus the example is nonlimiting.

The equipment includes stationary and portable detectors with one ormore sensors, some of which are non-contact sensors that are adjusted inthe X-Y-Z axes (which is sometimes also referred to as X1-X2-X3 axes)and with angular orientations relative to a line through a point on thesurface to a centerline of curvature of the surface. For example, FIG.21 illustrates an exemplary schematic of a system with a sensor fororientating to a curved surface. The system 2202 is used to measure anyexemplary three-dimensional curved surface 2204 of a material 2202 thatvaries in the X-Y-Z plane. A point 2206 on the surface 2204 is desiredto be analyzed as the scan is underway. A normal line 2207 to the pointis defined and a frame 2208 or other structure having one or moremembers 2210 for orthogonal movement and one or more members 2211 forangular movement orient a sensor 2212 so that the focus point 2214 isspatially position from the point 2206 and angularly aligned along thenormal line 2207 at theta and phi angles.

Additional information is found in PCT Application No. PCT/US13/033187,filed Mar. 20, 2013, and “Determining Composite Ply Orientations UsingUltrasonic Measurements,” Stair, S., Jack, D. A., and Fitch, J., ASMEIMECE, San Diego, Calif., Nov. 2013, both of which are incorporatedherein by reference.

While the disclosed embodiments have been described with reference toone or more particular implementations, those skilled in the art willrecognize that many changes are able to be made thereto withoutdeparting from the spirit and scope of the description. Each of theseembodiments and obvious variations thereof is contemplated as fallingwithin the spirit and scope of the claimed invention, which is set forthin the following claims.

What is claimed is:
 1. A system for testing composite materials,comprising: an ultrasonic transducer operable to scan a compositelaminate and produce composite scan data; a storage device connected toa processor, wherein the storage device includes an application tocontrol the processor; and wherein the processor receives the compositescan data from the ultrasonic transducer; wherein the composite scandata corresponds to a nonplanar surface of the composite laminate;wherein the processor is configured to generate a plurality of C-scanslices based on the composite scan data; wherein the processorautomatically determines at least one lamina property and at least onelamina failure parameter based on the composite scan data; wherein theprocessor is further configured to calculate a failure load for thecomposite laminate based on the at least one lamina property and the atleast one lamina failure parameter; and wherein the processor generatesa probabilistic failure envelope for the composite laminate using thecomposite scan data, the plurality of C-scan slices, the at least onelamina property, and the at least one lamina failure parameter.
 2. Thesystem of claim 1, wherein the processor is operable to calculate a plytype, a weave type, a number of individual laminas, or a thickness ofeach individual lamina using the composite scan data.
 3. The system ofclaim 2, wherein the processor is operable to determine fiber and matrixmoduli and/or the at least one failure parameter based on the ply type,the weave type, the number of individual laminas, or the thickness ofeach individual lamina calculated by the processor.
 4. The system ofclaim 2, wherein the failure load for the composite laminate is furtherbased on the ply type, the weave type, the number of individual laminas,or the thickness of each individual lamina calculated by the processor.5. The system of claim 1, wherein the ultrasonic transducer includes anultrasonic pulse-wave detector.
 6. The system of claim 1, furtherincluding a graphical user interface, wherein the graphical userinterface is operable to receive a z-start time and a z-gate time of theultrasonic transducer prior to scanning the composite laminate.
 7. Thesystem of claim 1, wherein the nonplanar surface of the compositelaminate has a three-dimensional curvature.
 8. A system for testingcomposite materials, comprising: transducer operable to scan a compositelaminate and produce composite scan data; and a processor, wherein theprocessor receives the composite scan data from the transducer; whereinthe processor generates at least one A-scan slice based on the compositescan data; a graphical user interface, wherein the graphical userinterface is operable to receive a z-start time and a z-gate time forthe transducer prior to scanning the composite laminate; wherein theprocessor generates at least one C-scan slice based on the at least oneA-scan slice; wherein the composite scan data corresponds to a nonplanarsurface of the composite laminate; wherein the processor is configuredto determine an orientation of each ply of the composite laminate; andwherein the processor generates a probabilistic failure envelope basedon the composite scan data, the at least one C-scan slice, the at leastone A-scan slice, and the orientation of each ply of the compositelaminate.
 9. The system of claim 8, wherein the processor generatessignal intensity data and signal time-of-flight data for a plurality ofspatial locations across a surface of the composite laminate.
 10. Thesystem of claim 9, wherein the processor is operable to determine fiberand matrix moduli and/or failure parameters based on a ply type, a weavetype, a number of individual laminas, or a thickness of each individuallamina calculated by the processor.
 11. The system of claim 9, whereinthe processor is operable to calculate a failure load for the individuallaminas based on the ply type, the weave type, the number of individuallaminas, or the thickness of each individual lamina calculated by theprocessor.
 12. The system of claim 9, wherein the nonplanar surface ofthe composite laminate has a three-dimensional curvature.
 13. A systemfor testing composite materials, comprising: a scanner operable to scana composite laminate and produce composite scan data; and a processor,wherein the processor receives the composite scan data from the scanner;wherein the composite scan data includes signal intensity and signaltime-of-flight data for a plurality of spatial locations across asurface of the composite laminate; wherein the composite scan datacorresponds to a nonplanar surface of the composite laminate; whereinthe nonplanar surface of the composite laminate has a three-dimensionalcurvature; wherein the processor generates at least one bulk propertyfor the composite laminate; and wherein the processor determines aprimary fiber orientation and a secondary fiber orientation based on thecomposite scan data.
 14. The system of claim 13, wherein the at leastone bulk property generated by the processor includes the extensionalstiffness, the bending stiffness, or the bending-extension couplingstiffness of the composite laminate.
 15. The system of claim 13, whereinthe processor generates a probabilistic failure envelope for thecomposite laminate based on the composite scan data.
 16. The system ofclaim 13, wherein the processor is operable to generate a ply type, aweave type, a number of individual laminas, or a thickness of eachindividual lamina.
 17. The system of claim 16, wherein the processor isoperable to determine fiber and matrix moduli and/or failure parametersbased on the ply type, the weave type, the number of individual laminas,or the thickness of each individual lamina calculated by the processor.18. The system of claim 16, wherein the processor is operable tocalculate a failure load for the individual laminas based on the plytype, the weave type, the number of individual laminas, or the thicknessof each individual lamina calculated by the processor.
 19. The system ofclaim 13, wherein the processor determines a primary fiber orientationand a secondary fiber orientation for each C-scan of the plurality ofC-scans.
 20. The system of claim 13, wherein the processor is furtheroperable to generate at least one A-scan slice, wherein the processor isoperable to generate at least one C-scan slice based on the at least oneA-scan slice, and wherein the processor is operable to analyze the atleast one A-scan slice, the at least one C-scan slice, and the compositescan data to generate a failure envelope for the composite laminate.